1. Field of the Invention
This invention relates to evaporation coating of a high-carbon high-chromium steel with carbide or nitride of titanium.
2. Description of the Prior Art
As means for enhancing the wear resistance, corrosion resistance and heat resistance of a metallic material, there is a method of evaporating carbide or nitride of titanium. A coat of titanium carbide or nitride has an extremely high hardness (TiC: Hv 3300-4000, TiN: Hv 1900-2000) as well as corrosion resistance and heat resistance, and is therefore used particularly for reinforced plastic extruder screws, corrosion-, heat- and wear-resistant tools (for instance, forming and guide rolls, powder compacting dies, plastic working tools), etc.
As a parent material to be coated with the carbide or nitride of titanium, a material having a strength suitable for making the most of the hardness of the coating is selected. For corrosion- and wear-resistance use, particularly, a high-carbon high-chromium steel such as JIS SUS440C is used. High-carbon high-chromium steels have sufficient strength and hardness for supporting the above-mentioned coating. When the high-carbon high-chromium steel coated with titanium carbide or nitride is applied to corrosion-resistance use, the steel is capable of preventing the problem that the coated member may become unusable due to fracture of the coating as a result of rapid progrss of corrosion from a broken portion of the coating, because the steel is not so inferior to the coating in corrosion resistance. Conventional materials coated with TiC and/or TiN, however, have difficulties in that the coating will flake or be broken relatively early, and are therefore not satisfactory.